A major challenge in engine oil formulation is simultaneously achieving wear and deposit control, and oxidation stability, while also maintaining fuel economy performance, over a broad temperature range.
Lubricant-related wear control is highly desirable due to increasing use of low viscosity engine oils for improved fuel efficiency. As governmental regulations for vehicle fuel consumption and carbon emissions become more stringent, use of low viscosity engine oils to meet the regulatory standards is becoming more prevalent. At the same time, lubricants need to provide a substantial level of durability and wear protection due to the formation of thinner lubricant films during engine operation. As such, use of antiwear additives in a lubricant formulation is the typical method for achieving wear control and durability. Due to limitations of using high levels of some antiwears due to catalyst poisoning and deposit formation, it is highly desirable to find alternative methods for achieving excellent wear control and durability without poisoning the catalyst.
Most current antiwear additives contain metals, phosphorous and/or sulfur. Zinc dialkyl dithiophosphate (ZDDP) is a common antiwear additive used in engine lubricants. However, these elements are known to harm catalysts used to treat exhaust gases from internal combustion engines, and thus antiwear additives which are free of metals, sulfur and phosphorous will be advantaged in the marketplace.
It is also beneficial that additives used to improve lubricant performance form stable solutions or dispersions without rapidly dropping out.
Despite advances in lubricant oil formulation technology, there exists a need for a homogenous, compatible engine oil lubricant that effectively improves wear control while maintaining or improving fuel efficiency.